The invention relates to a device for blowing out hollow bodies, as for example preforms for plastic containers, in a conveyor assembly, wherein the hollow bodies are open at one end and are closed at the other end, and comprise at the open end a head with a collar, wherein the conveyor assembly comprises a transport line with feed rails being inclined in the conveying direction, wherein the hollow bodies are supported on the feed rails with the collar and with the open end upwardly directed, and are arranged in a row with an axial distance to one and another and are conveyed along the transport line and wherein a facility for blowing a gas stream into the hollow space of the hollow bodies is arranged in a partial area of the transport line.
Devices for cleaning hollow bodies, as for example bottles or preforms for plastic bottles, through flushing respectively blowing out the hollow space of such hollow bodies with water and/or a gas stream are known in production lines for such containers. From U.S. Pat. No. 6,173,827 a device for cleaning the hollow space of preforms made of plastics for plastic bottles is known. Such preforms are regularly cylindrically shaped hollow bodies with an open and a closed end, which comprise a collar in the area of the open end which comprises a larger diameter than the rest of the hollow body. These preforms are correctly positioned in generally known assemblies and are arranged in a row. This row of an adjacently arranged preforms is conveyed in the described device on an sloped chute with rails, also known as feed rails, from a processing station to a subsequent processing station, e.g. a plastic blow moulding machine. These feed rails thereby form a transport line of a conveying assembly. In a partial area of this transport line, respectively this sloped chute, in which the preforms are supported with their collars on the support rails, a device for cleaning the preforms is arranged. In this device the preforms are turned by 180°, such that their opening is downwardly directed and the preforms are thereby further conveyed in transport direction. Below the preforms and with a distance thereto, multiple nozzles are arranged through which ionized gas is blown into the hollow space of the preforms. Through the ionized gas electrostatic loads are neutralized and possible dirt particles and impurities in the hollow space of the preforms may fall out downwardly. Subsequently, the preforms have to be turned again by 180° such that they, again in the correct position, may be transferred with outwardly directed opening to the feed rails. The turning of the preforms according to this solution requires extensive measures as well as an additional assembly, which interrupts the feed rails and in view of the increasingly higher conveying speeds and also as a consequence of the continuously lighter preforms the transportation is very difficult and partially impossible.
DE 101 40 906 A1 discloses a further method and a device for cleaning hollow preforms made of plastics. In this solution the preforms are taken over by an infeed star wheel from a conveyor channel and are sorted and separated. Subsequently, the preforms are transferred to a star wheel in which they are supported by means of their collar in a vertically hanging manner, wherein the open end is upwardly directed. Across a partial area of the star wheel a device is arranged by means of which a lance may be moved into the hollow space of the preform, wherein this lance comprises an air nozzle at the front end. Via this lance ionized air is blown against the closed end of the preform, which then flows out between the wall of the preform and the lance and is sucked-off above the open end of the preform. This lance has to run over a certain period of time synchronically with the star wheel respectively the preforms in the conveying direction and has to be moved into the preforms, stopped and retracted again during this time span. In this device the preforms do not have to be turned. However, it has the disadvantage that the conveying channel and thus the transport flow is interrupted by the star wheel, which represents an additional source of failure. Moreover, the assembly of the star wheel and the related device with the extendible/retractable lances is extremely extensive and failure prone and the effort for the mechanics and the control becomes very high.
In order to save raw material and production costs, it is attempted to produce hollow bodies from plastic material and therefore also the respective preforms with thinner walls and lighter. The result is, that the handling of the preforms in automated transport devices becomes increasingly difficult and failure prone. It is therefore desired, not to interrupt the transport flow of the hollow bodies, e.g. of the preforms, for the blow out procedure and to integrate the blow out procedure into the normal conveying movement of the preforms.